The term “grouping” refers to the practice of arranging a plurality of predetermined devices into a single group so that contents may be exchanged freely between the grouped devices. Conventionally, grouping has been implemented by assigning a group key to each group of devices.
One disadvantage with the assigning of group keys in grouping is that the more complex the configuration of a given group becomes, the more complicated the structure of the required group key turns out to be for the group in question. The complicated group key structure can be a significant handicap in system design.